In the quest for hard surface cleansers which have efficacy against a variety of soils and stains, various heavy duty liquid cleansers have been developed. As an example, U.S. Pat. No. 3,985,668 issued to Hartman, shows a combination of perlite (an expanded silica abrasive, which is here used as a filler), a colloid-forming clay, in combination with a hypochlorite bleach, a surfactant and a buffer in which abrasives are suspended. A clay thickened system of this type tends to set up or harden upon storage due to the false body nature of the thickeners. They require shaking before use to break down the false body structure. Further prior art cleansers which attempt to suspend abrasives use either inorganic colloid thickeners only or mixed surfactant thickeners at high levels of surfactants. Additionally, syneresis becomes a problem as the solids portion of such cleansers substantially separate from the liquids portion. One way to alleviate this is to use a perlite type material with specified particle size as defined in U.S. Pat. No. 3,985,668, issued to Hartman. Additionally, high levels of surfactants can be used to form a plastic rheology for suspension of abrasives. However, they also have a detrimental effect on hypochlorite stability. These mixed surfactant thickened compositions, for example, U.S. Pat. No. 4,352,678, issued to Jones et al, have been used to suspend abrasives and incorporate a source of hypochlorite bleach. However, this particular cleanser must incorporate large amounts of surfactants in order to suspend abrasives. This has the unfortunate disadvantage of resultant poor hypochlorite stability in terms of half-life stability at 50.degree. C. for low levels of hypochlorite (0.5% sodium hypochlorite initial level). For the instant purpose, half-life stability is defined as the amount of time it takes for 50% of the initial amount of bleach present in a given composition to decompose.
Other efforts in the cleanser field have included: U.S. Pat. No. 4,337,163, issued to Schilp, which related to a bleach thickened with a combination of amine oxides and anionic surfactants. Abrasives are unable to be suspended in the Schilp formulas. U.S. Pat. No. 4,287,079, issued to Robinson, on the other hand, related to a clay/silicon dioxide thickened, bleach-containing abrasive cleanser which could contain an anionic surfactant. Due to the clay-thickened rheology, cleansers of this sort quickly dry out and set up. While these type of cleansers thus become less flowable over time, they are unfortunately also plagued by significant syneresis problems. U.S. Pat. No. 3,956,158, (also British Patent No. 1,418,671) issued to Donaldson shows an abrasive-containing bleach thickened with insoluble detergent filaments. As described in U.S. Pat. No. 4,352,678, compositions such as those disclosed in U.S. Pat. No. 3,956,158 have numerous disadvantages, including low detergency and lack of physical and chemical stability at higher temperatures. Lastly, U.S. Pat. No. 3,558,496, issued to Zmoda, shows a hypochlorite bleach thickened with negatively and positively charged clays. Negatively charged clays include smectites, montmorillonites, etc., which are common clays. The positively charged clay was a fibrillar aluminum oxide. Again, due to presence of the former clays, a false body rheology is likely to occur in which hardening soon occurs and probable increased syneresis is observed.
U.S. Pat. Nos. 4,599,186, 4,657,692 and 4,695,394, all issued to Choy et al, and of common assignment herein, represent significant steps in achieving good physical and chemical stabilities of liquid abrasive cleansers containing bleach. The disclosures of these patents are incorporated herein by reference. These patents teach the use of an inorganic colloid combined with a surfactant/electrolyte system to provide good physical stability. However because the inorganic colloid in these cleansers is basically insoluble in aqueous dispersion and must rely on its interaction with surfactants and electrolytes to maintain suspension, phase separation between the liquid, continuous phase and the solid, discontinuous phase can occur, especially under elevated temperatures and extended storage times.
Consequently, there is still a need for ways in which to maintain long-term physical stability in liquid abrasive cleansers which contain bleach.